There are many studies in social sciences, such as traffic accident analysis, in which
the event counts may be characterized by a large number of zero observations. In this
article, a proposed model that takes into account both the zero-count state and the nonzero-
count state is used to describe the traffic accident phenomenon. The probability of
the zero-count state (p) and the mean number of event counts (μ) in the non-zero-count
state may depend on the covariates. Sometimes, p and μ are unrelated, while at other
times, p may assume a simple function of μ. In proposing the model, different types of
traffic accidents at signalized intersections in Singapore were investigated. The results
demonstrate that the zero-altered probability process is an appropriate technique for
modeling specific types of accidents in which the data contain many zero counts.